The present invention relates to optical waveguide grating devices. Such a device comprises an optical waveguide, such as an optical fiber, in which a grating has been formed in order to affect the optical characteristics of the waveguide. The invention is especially suited for providing an athermalized optical waveguide grating wherein temperature varying properties are controlled.
The central wavelength of optical waveguide grating devices such as a fiber Bragg grating can be altered by changing the temperature of the optical waveguide fiber Bragg grating. The central wavelength can also be altered by changing the stress/strain in the fiber that contains the Bragg grating. To minimize any undesired wavelength shifts due to temperature variations the fiber Bragg grating device can be rigidly attached, under appropriate tension, to a substrate material having a suitable negative coefficient of thermal expansion. Low softening temperature phosphate glass frits which have been filled with a pyrophosphate glass-ceramic have been used to attach fibers to negative expansion beta-eucryptite substrates. The inventors have discovered that such frits, while operable, may develop stresses due to expansion differences during the process steps of making a device which may lead to a stress build up in the components that may be undesirable.
Accordingly, the present invention is directed to an optical waveguide device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. The present invention provides an improved athermal optical waveguide grating device.
In one aspect, the invention is directed to improvements which reduce stress build up caused by differential expansion of components during manufacture and subsequent use.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the apparatus, process, and compositions particularly pointed out in the written description and claims hereof, as in well as the drawings.
To achieve these and other advantages, and in accordance with the purpose of the invention, as embodied and broadly described, the invention comprises an optical waveguide device which includes an optical waveguide grating member held under tension, which is secured to a supporting member such that the supporting member reduces the tension that the grating member is held under in relationship to a temperature increase of the device, with the grating member secured to the supporting member with a securing glass having a linear coefficient of thermal expansion ranging from 1xc3x9710xe2x88x927/xc2x0 C. to 10xc3x9710xe2x88x927/xc2x0 C. in the temperature range of 0xc2x0 C. to 300xc2x0 C.
In another aspect, the invention includes an athermalized optical waveguide device which includes an optical waveguide reflective Bragg grating member and a negative thermal expansion support member with the grating member secured to the support member with a copper alumino silicate glass.
In an additional aspect, the invention comprises an optical waveguide device which includes a negative thermal expansion longitudinal body substrate with a first end, and a second distal end distal (at a distance) from the first end, with the substrate defining a first solid insert receiving void, proximate the first end and a second solid insert receiving void proximate the second end. The device further includes a first solid insert member received within the first solid insert receiving void and a second solid insert member received within the second solid insert receiving void, and a longitudinal optical waveguide grating member held under a tension with the grating member secured to the first solid insert member and to the second solid insert member, wherein the negative thermal expansion substrate reduces the tension, under which the grating member is held, in relationship to a temperature increase of the device.
In another aspect, the invention comprises a method of making an optical waveguide device which includes the steps of providing an optical waveguide grating member, providing a negative thermal expansion supporting member, tensioning the grating member, and securing the grating member to the negative thermal expansion supporting member with a copper alumino silicate glass.
An additional aspect of the invention includes a method of making an optical waveguide device which comprises the steps of providing an optical waveguide grating member, providing a negative thermal expansion substrate, forming a first and a second insert receiving void in the negative thermal expansion substrate, inserting a first solid insert member in to the first insert receiving void and inserting a second solid insert member into the second insert receiving void. The method further includes the steps of tensioning the grating member and securing the grating member to the first solid inserted insert member and to the second solid inserted insert member wherein the negative thermal expansion substrate reduces the tensioning of the grating member in relation to a temperature increase of the device.
An additional aspect of the invention includes an optical waveguide device including an optical waveguide grating member held under tension by bonding the member to a negative thermal expansion substrate with a copper alumino silicate glass.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed.